Epithelial transport of drugs in cell culture. II: Effect of extracellular calcium concentration on the paracellular transport of drugs of different lipophilicities across monolayers of intestinal epithelial (Caco-2) cells (original) (raw)
1990, Journal of Pharmaceutical Sciences
Abatract 0 A human intestinal cell line, Cam-2, was used as a model to study the passive diffusion of drugs across intestinal epithelium. The cells formed continuous monolayers when grown on permeable filters of polycarbonate. After 10 days in culture, the monolayers had a transmembrane resistance of -260 ohmscm2 and a cell density of 0.9 x 10' cellslcm2. At this time the cells were impermeable to ["CJpolyethyleneglycol (MW 4000). These characteristics remained constant for 20 days (i.e., from day 10 to day 30). Six beta-blocking agents with a 2000-fold range of lipophilicity were studied for their transepithelial transport properties. The transport parameters were independent of drug concentration and transport direction. The apparent permeability coefficients ranged from 41.91 t 4.31 x lo-' cm/s for the most lipophilic drug, propranolol, to 0.203 2 0.004 x lO-'cm/s for the most hydrophilic drug, atenolol. The transport parameters were compared with those published for rat ileum. Drugs and Radiolabeled MarkereSH-Labeled and unlabeled atenolol (specific radioactivity 0.627 nCi/nmol), H216/44 [(S)-4-hydroxy-N-~2-((2-hydroxy-3-(4-~2-~2-~cyclopropylmethoxy)ethoxy)ethyl)phenoxy)-propyl)amino)ethyl)-l-piperidinecar~x~ide; specific radioactivity 16.7 pCi/nmoll, alprenolol (specific radioactivity 0.252 nCi/nmol), and metoprolol (specific radioactivity 0.475 pCi/nmol, as well as "C-labeled practolol (2.1 nCi/nmol) were generous iRs from Dr. KurtJtirgen Hoffman, AB HBssle, GBteborg, (MW 4000; specific radioactivity 15.0 Ci/mg) were obtained from New England Nuclear, Boston, MA. The radiolabeled compounds had a radiochemical purity of 96-99%, Propranolol and alprenolol were purchased from Sigma Chemical Company, St. Louis, MO. Octanol-water distribution coefficienta (0) and PK, values for the pblockers were kindly provided by Dr. KurtJtirgen Hoffman, AB Hlssle, GBteborg, Sweden, and have also been published elsewhere.1"14 Cells-Caco-2 cells, originating from a human colorectal carcinoma,lb were obtained from American Tissue Culture Collection, Rockville, MD. The cells were maintained in Dulbecco's modified Eagle medium (DMEM) containing 10% fetal calf serum, 1% nonesaential amino acids, benzylpenicillin (100 U/mL), and streptomycin (10 pg/mL). Cells of passage number 85-95 were d. All tissue culture media were obtained from Gibco through Laboratorie Design AB, Lindingo, Sweden. The medium was changed every eecond day.